Tirzepatide is one of the most-studied metabolic peptides of the last decade, but the science it’s built on goes back more than fifty years. It didn’t appear fully formed. It sits on top of two hormones that researchers spent decades arguing over, a bold idea about combining them into one molecule, and a long clinical program run under the code name LY3298176. Here’s the story of how a single 39-amino-acid peptide came to be.
The incretin groundwork (1970s–1980s)
Long before anyone drew up tirzepatide, researchers were working out why the gut has such a strong say in blood sugar. Food taken by mouth triggers a far larger insulin response than the same amount of glucose given intravenously. That gap became known as the incretin effect, and the hunt was on for the hormones behind it.
The first break came in the early 1970s, when John Brown and colleagues isolated a gut peptide and characterised it. Initially tagged for its ability to slow stomach acid, it was later understood to be a potent driver of meal-triggered insulin release, and was renamed glucose-dependent insulinotropic polypeptide, or GIP. The second incretin took another decade. In the mid-1980s, work on the proglucagon gene by researchers including Joel Habener and Svetlana Mojsov identified glucagon-like peptide-1 (GLP-1) as a cleavage product of that precursor. Two hormones, both released from the gut after eating, both nudging the pancreas to release insulin only when glucose is high.
One molecule, two receptors (2013)
For years GLP-1 got most of the drug-development attention. The idea that you could hit both receptors at once with a single engineered peptide was the pivotal turn. In 2013, Brian Finan, Richard DiMarchi, Matthias Tschöp and co-workers published a paper in Science Translational Medicine describing a “unimolecular” dual incretin, a single peptide built from an intermixed GLP-1 and GIP sequence that activated both receptors. In their rodent, monkey and early human work, the co-agonist outperformed selective single-target peptides on measures of body composition and glucose handling. The term “twincretin” stuck. It was proof of concept that the two incretin pathways could be combined by design rather than by giving two separate drugs.
LY3298176 and the discovery paper (2018)
Eli Lilly ran with the dual-agonist concept and engineered its own candidate: LY3298176, the compound now known as tirzepatide. It’s a synthetic 39-amino-acid peptide whose backbone is based on the GIP sequence, modified to also engage the GLP-1 receptor, and fitted with a C20 fatty di-acid chain that lets it bind albumin and stay in circulation long enough for once-weekly dosing in trials.
The foundational description came in 2018, when Tamer Coskun and colleagues published “LY3298176, a novel dual GIP and GLP-1 receptor agonist for the treatment of type 2 diabetes mellitus: from discovery to clinical proof of concept” in Molecular Metabolism. That paper walked the molecule from its receptor pharmacology through first-in-human dosing. In the Phase 1 work reported around that time, single subcutaneous doses were given to healthy volunteers with dose escalation into people with type 2 diabetes. Phase 2 studies through 2018 and 2019 followed, and researchers reported dose-dependent reductions in HbA1c and body weight in study participants.
The SURPASS and SURMOUNT trials (2021–2023)
The large Phase 3 evidence base arrived under two program names. The SURPASS trials studied tirzepatide in type 2 diabetes. SURPASS-1 was published in The Lancet in 2021. SURPASS-2, published in The New England Journal of Medicine in 2021, compared tirzepatide against injectable semaglutide 1 mg; in that study researchers reported greater reductions in HbA1c and body weight for tirzepatide across its doses.
A separate program, SURMOUNT, examined the compound in the context of obesity. SURMOUNT-1, led by Ania Jastreboff and colleagues and published in The New England Journal of Medicine in 2022, reported mean body-weight reductions ranging from roughly 16% to 22.5% depending on dose over 72 weeks. On the regulatory side, the U.S. FDA cleared tirzepatide for type 2 diabetes under the brand Mounjaro on 13 May 2022, and for chronic weight management under the brand Zepbound on 8 November 2023. Later work extended into conditions such as obstructive sleep apnea, and research on the molecule remains active across multiple metabolic areas.
Where the science stands
Tirzepatide’s arc is unusual in how directly it traces to basic hormone biology: two incretins mapped out across the 1970s and 1980s, a dual-agonist concept proven in 2013, a specific engineered peptide characterised in 2018, and a decade of trial data behind it. It was the first molecule of its dual-receptor class to move through that full pipeline, which is why it comes up so often as a reference point in incretin research.
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Research use only
Tirzepatide is supplied by Vero Labs strictly as a research compound for laboratory and research use only. It is not for human or animal consumption, and nothing above is medical advice or a description of outcomes any individual should expect. Every batch is independently third-party lab-tested, with a published Certificate of Analysis (COA) available for the material we supply.